EFFECT OF PROBIOTIC ADMINISTRATION ON DIARRHEA INCIDENCE, SEVERITY, AND THE FECAL MICROBIOME IN NEONATAL FOALS

An experiment was conducted to investigate the effects of probiotic supplementation on diarrhea incidence and severity in neonatal foals, and to characterize the bacterial population in the neonatal gut related to “foal heat” diarrhea. Twenty-four stock-type newborn foals were used in a completely randomized design. Foals were enrolled in the trial within 24 h of age and randomly assigned to treatment; control (C) or probiotic (P). Animals assigned to P received 6 g of Pro Biostatin® containing 500 ×106 cfu/g Kluyveromyces fragilis B0399 and Saccharomyces cerevisiae 1026 orally twice daily for 14 d. The trial began in February and ended in June, 2016, with each foal enrolled from birth to 28 d of age. Fecal samples were collected from foals at d 0, 7, 14, 21, and 28 and a corresponding mare fecal sample was collected on d 28 by the consulting veterinarian or trained farm staff. Blood was collected on d 0, 7, 14, 21, and 28 and analyzed using IDEXX ProCyte Dx® Hematology Analyzer (IDEXX Laboratories, Westbrook, Maine) to determine complete blood count variables. Additionally, health observations were made daily and foal feces were scored using a 3-point system (0 to 2) based on severity. Fecal samples were sent to the University of Arkansas Animal Science lab for DNA sequencing and microbiome analysis. Diarrhea was observed in 95% of foals throughout the study. There was a trend for a main effect of treatment on the incidence of diarrhea in neonatal foals (P = 0.105). A
numerical difference was observed in the length of diarrhea bouts, which decreased with subsequent diarrhea events. There was no effect of probiotic treatment on diarrhea severity in neonatal foals (no diarrhea, P = 0.522; mild diarrhea, P = 0.267; and severe diarrhea, P = 0.333). However, foals developed severe diarrhea within the first 14 d postpartum. There was a treatment × day interaction for certain CBC variables; RBC (P = 0.024), and hemoglobin (P = 0.049) concentration, hematocrit percentage (P = 0.037), and platelet volume (P = 0.012). Additionally, there was a main effect of d on all red blood cells (RBC, P = <.0001) and all white blood cells (WBC, P = 0.0053) except lymphocyte concentration. The predominant bacteria phylum identified in the feces was Firmicutes and Bacteroidetes. The trend was similar for all animals. As foals matured, bacterial community structure and diversity also became more enriched and began to approach a similar community structure as their dam. Results from this study indicate that administration of a probiotic containing 500 × 106 cfu/g Kluyveromyces fragilis B0399 and Saccharomyces cerevisiae 1026 had a tendency to decrease diarrhea incidence but did not significantly affect diarrhea severity in neonatal foals. Future research is needed to further elucidate the role of the intestinal microbiome in neonatal foal heat diarrhea and potentially identify novel bacteria candidates that may have beneficial probiotic effects.